Breech block locking means



y 1956 B. MAILLARD 2,756,640

BREECH BLOCK LOCKING MEANS Filed March 50, 1951 2 Sheets-Sheet 2 lfIVtWTO/7 m ATMRNEY United States Patent BREE'CH BLOCK LOCKING MEANS Bernard Maillard, Geneva, Switzerland, assignor to Society Brevets Aero-Mecaniques, S. A., Geneva, Switzerland, a society of Switzerland Application March 30, 1951, Serial No. 218,370 Claims priority, application Luxembourg March 30, 19 50 2 Claims. (Cl. 89--187) The present invention relates to self-loading fire-arms (this term being meant to include both semi-automatic firearms which require a separate trigger-pull for every shot, and automatic firearms, which fire bursts, and also double action arms capable of working either in semiautomatic or in fully automatic fashion) in which the breech block structure is held temporarily locked in bore closing or active position by a longitudinal sliding unit carrying the striker and capable, once said breech block structure has reached said active position, of further moving toward the front to perform this temporary locking action and to fire the cartridge.

Its chief object is to provide a firearm of this kind which is better adapted to meet the requirements of practice than those used up to the present time, and, in particular, such that the breech mechanism movable elements are of lighter weight, which makes it possible to achieve higher rates of fire.

According to the invention, this breech block structure is constituted by at least one element carried by said sliding unit and movable transversely with respect thereto into direct locking engagement with the breech, case, this transverse movement of said element being produced by said sliding unit as it starts on its supplementary frontward displacement.

Preferred embodiments of my invention will be hereinafter described with reference to the accompanying drawings, given merely by way of example and in which:

Figs. 1 and 2 show, with some parts removed, respec tively in elevation with portions in section on the line II of Fig. 2 and in plan view with portions in section on the line IIII of Fig. l, the breech mechanism of an automatic cannon made according to my invention.

Fig. 3 is a plan view, on a smaller scale and partly in section through the horizontal axial plane of the barrel, of the sliding system of this mechanism. 1

Fig. 4 is a perspective view, with portions cut away, of said breech mechanism.

Fig. 5 shows a modification of some parts of this mechanism.

The following detailed description relates to the construction of a small bore automatic cannon.

Automatic firearms of the kind with which my invention is concerned include a breech mechanism constituted essentially by a sliding breech block the front edge of which is applied, at the end of its frontward stroke, against the rear wall of the cartridge present in the firearm cartridge chamber. Said breech block is temporarily held in this position by at least one locking member bearing against the breech case and subjected to the action of a sliding unit which carries the striker and has, with respect to the breech block after said block has reached the end of its frontward stroke, a supplementary 2 desirable, and this in particular for automatic cannons of a bore higher than 20 millimeters.

This results in particular from the following facts:

The inertia of the breech block proper, the mass of which is relatively greater than that of the other reciprocating parts, opposes acceleration of the rate of fire.

The recoil movement of the sliding unit, imparted thereto either through a gas tap or by making use of energy supplied by the recoil of the firearm, gives rise, when said unit strikes the breech block at the time said block is being unlocked, to a shock followed by a short stoppage which unnecessarily occupies a non negligible portion of the time available between two consecutive rounds and therefore opposes the possibility of obtaining high rates of fire.

Finally, the relatively great distance between the front edge face of the breech block (which receives the thrust exerted by the rear wall of the cartridge when the round is fired) and the surface of the breech case on which the locking member is bearing, unavoidably causes local and temporary deformations due to warping, elongation and compression effects, which interfere with the working of the firearm during the unlocking period.

I will now describe how the construction according to my invention eliminates the above stated drawbacks.

As usual, the firearm includes a barrel 1, preferably removable, extending rearwardly to form a breech case 2.

The breech mechanism includes the following parts:

On the one hand at least one and preferably (as hereinafter assumed) two locking breech block elements 3a and 3b capable of moving transversely between a retracted and unlocked position (shown by Figs. 3 and 5) in which they can reciprocate inside breech case 2, and an active locked position (shown by Figs. 2 and 4) in which they bear upon said breech case, preferably against distinct abutments 4 made of an especially hard metal, the front edges of said breech block elements then constituting the bearing surface which temporarily closes the firearm cartridge chamber behind the rear wall 5a of the cartridge case 5 in firing position;

And, on the other hand, a sliding unit 6 serving to support both locking breech block elements 3a and 3b slidable thereon and a striker 7. This unit 6, which is urged frontwardly by return means which will be more explicitly referred to hereinafter, is adapted to have, once said locking breech block elements 3a and 3b have reached the end of their frontward stroke,-a supplementary frontward displacement intended first to bring said breech block elements into their locked position, then to hold them in this position and finally to fire the cartridge.

Locking breech block elements 3a and 3b may then be constituted by two similar pieces mounted symmetrically with respect to the longitudinal plane of symmetry of the firearm and having front edge lines held adjacent to each other along a vertical line XX, the movements of Said elements from their retracted unlocked position to their expanded locked position and vice versa being obtained by horizontal pivoting thereof about vertical line XX (of course the terms horizontal and vertical are used on the assumption that the arm barrel is horizontal and its longitudinal plane of symmetry is vertical).

The sliding unit 6 is arranged to act, in the course of its supplementary frontward stroke, as a wedge between said elements 3a and 3b so as to cause them to pivot about line XX until they bear against abutments 4.

The inner walls of breech block elements 3a and 3b form, opposite block 6, recesses leaving between said elements a space C the horizontal section of which decreases gradually toward the front, as clearly shown on Fig. 2 for member 3a and on Fig. 3' for member 3b.

The sliding unit is constituted by two bars 6a guided longitudinally in slideways 2a provided for this purpose in the breech case, said sliding bars being interconnected by a cross piece 6b which carries the block 6 which forms the active element (with respect to elements 3a and 3b) of said sliding unit.

Block 6 is provided with vertical shoulders S inclined outwardly toward the rear and adapted to bear, as long as elements 3a and 3b are in retracted position, against surfaces s of corresponding inclination carried by said elements, the supplementary frontward stroke of the sliding unit producing, through a cam effect exerted by shoulders S on surfaces s, the outward transversepivoting of elements 3a and 3b which have then reached the end of their frontward stroke and have thus been brought into active position (the position of the respective parts when shoulders S start acting on surfaces s is shown by Fig. 3 and the position of the same parts once locking has been performed is shown by Fig. 2)

The sliding unit carries, on the one hand, near the rear end thereof and preferably on block 6 proper, trigger stops 6c and, on the other hand,.near the front end thereof and preferably on cross plate 6b, two projections 6d (shown on Fig. 4) which determine the limit frontward position of elements 3a and 3b with respect to unit 6 during the recoil of the reciprocating breech parts and imperatively compel said elements 3a and 3b to move toward each other at the beginning of the recoil stroke of the sliding unit.

I further provide, in the central region of the front edges of said elements 3a and 3b, a passage for the point of striker 7.

It should be noted that I might also, according to a modification illustrtaed by Fig. 5, substitute for shoulders S rollers 8 cooperating with the surfaces .9 of elements.

3a and 3b.

Anyway, the semi-circular portions Ta and Tb of the front faces of elements 3a and 3b, which are to consti-. tute the bearing surface for the rear Wall 511 of the cartridge when said elements are in front position, must be located in the same plane when the locki-ngbreech block elements occupy their locked position, whereby said cartridge rear wall is then supported over its whole area (position shown for member 3a on Fig. 2). Surfaces Ta and Tb will therefore form a dihedral angle when elements 3a and 3b are retracted, as shown by Fig. 3.

On the other hand, due to the fact that elements 3a and 3b are still retracted when they must, by means of their front edges, push a fresh cartridge into the cartridge chamber, it is of interest to provide said front edges, above semi-circular surfaces Ta and Tb, with plane surfaces tar and lb the planes of which form, with those of said surfaces Ta and Tb, an angle such that said surfaces ta and ti; are located in the same plane whenelements 3a and 3b are retracted, and can thus bear through their Whole area against the rear wall on the fresh cartridge to be fed (position shown by Fig. 3).

This firearm is further provided on the one hand with an extractor 9 mounted, as will be more explicitly explained hereinafter, in cross piece fashion between elements 3a and 3b and, on the other hand, with a control device capable of producing after the firing of every round, a recoil displacement of the sliding unit against the action of a recuperator system intended to achieve the frontward return movement of said sliding unit.

Concerning first extractor 9, it is arranged in such manner that its nose 9a projects to the front of the front edge of elements 3a and 3b and to the inside of the periphery of bearing surfaces Ta-Tb.

Extractor 9 includes a transverse trunnion 9b the journal portions of which engage in housings 10 provided for this purposein elements 3a and 3b.

These journals and housing are arranged in such manner as to make allowance for the pivoting movements of elements 3a and 3b, for which purpose, for instance.

and as shown by Fig. 5, the journal surfaces of the trunnion are made of straight cylindrical shape over their whole length and housings 10 are given a flaring shape (from their orifice toward their bottom) whereby the journals of the trunnion bear against the front portion of housings 10 when elements 3a--3b are retracted to vide two springs 11 housed inlongitudinal bores formed for this purpose respectively in each of the elements 3;:

. and 3b, said springs further tending, due to the fact that their lines of action are oblique with respect to axi XX, to move said elements 311 and 3b away from each other. It should be noted that the trunnion also has the function of keeping the two elements 311 and 3b exactly opposite each other, with their vertical edge lines in contact along XX.

Concerning now the device for operating sliding unit 6, it is preferably of the type acting by tapping of gas from the firearm barrel.

' housed in the breech case, it seems preferable to arrange said control device according to a particular feature of my invention, applicable to all firearms having a sliding unit intended temporarily to keep the breech mechanism in locked position.

According to this feature, I convey, through a system of conduits 12, the gases tapped from the firearm barrel toward two chambers of variable volume 13, of quadrangular section, provided in the breech case and the movable wall of which is constituted by the front edge of sliding bars 6a, said chambers 13 being. consequently located near the front of the breech case in line with the sliding bars 6a of sliding unit 6.

Concerning the recuperator system, which is to return said sliding unit frontwardly, it is preferably made, according to another feature of my invention, independent of the preceding ones, in such manner that it cooperates with the unit in question not directly but through an intermediate part having a movement simultaneous with that of the sliding unit but of smaller amplitude, whereby it is possible to reduce the overall dimensions of the firearm.

For this purpose, as shown by the drawings, I provide each sliding bar 6a with a rack 14 meshing with a pinion 15 carried by a sliding member 16, preferably of cylindrical shape, movable in a longitudinal bore provided for this purpose in the breech case, said pinion 15 rolling on a fixed rack 17 carried by said breech case.

Each sliding member 16, the displacements of which are of an amplitude equal to one half of that of sliding unit 6, cooperates with a return spring 18 housed in the guiding bore of the sliding member.

It should be noted that it will be further of interest to provide, in the usual manner, near the rear of the firearm, an accelerator elastic system (not shown) capable of reinforcing the action of springs 18 by giving sliding unit 6, when it comes near the end of its rearward stroke, a frontward impulse.

This automatic cannon works as follows:

The sliding unit, which is supposed to start from its extreme rear position (the triggers being depressed) is moved frontwardly by return springs 18, elements 3a and 3b being then located in the retracted position shown by Fig. 3.

Once elements 3a and 3b have reached their limit frontward positions, sliding unit 6 starts on its supplementary frontward displacement, shoulders 5 pushing said elements 3a and 312 into locked position (as shown by Fig. 2) and finally, striker 7 strikes the rear part 54 of the cartridge already housed in the cartridge chamber, thus firing the shot. During the whole of the supplementary stroke of sliding unit 6, subsequent to the bringing of elements 3a and 312 into active position, said unit opposes any unlocking of said elements.

The gases tapped from the arm barrel then act directly upon the front edges of sliding bars 611 and cause the sliding unit to recoil and, when it has moved rearwardly a suflicient distance, this unit ceases to hold elements 3a and 3b. Due to the fact that the slope angle of abutment 4 is reversible, the thrust exerted by the cartridge case, in combination with the action of projections 6d, compels elements 3a and 3b to retract toward each other and then to slide rearwardly together with the sliding unit. In the course of this recoil movement, the extractor catches the spent cartridge case which is expelled through the action of a mechanism not shown by the drawingv When the recoil movement is finished and supposing that the triggers have not been released, the whole of the sliding unit 6 and elements 311 and 3b starts back in the frontward direction under the combined actions of the accelerator system and return springs 16. The same cycle of operations is then repeated.

The chief advantages of my system are its simplicity, its light weight and its performance, especially concerning the rate of fire.

These advantages result in particular, as already above explained, from the fact that the conventional heavy breech block is replaced by light elements which are locked directly on the breech case, from the small length v of these elements and from the direct pneumatic control of the sliding unit.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and etficient embodiments of my invention, it should be well understood that I do not Wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts Without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

What I claim is:

. 1. A self loading firearm which comprises, in combination, a barrel, a breech case rigid with said barrel at the rear end thereof, a breech mechanism including at least one sliding piece movable with respect to said breech case in response to the operation of said firearm, with a reciprocating motion parallel to the axis of said barrel, at least one rack rigid with said breech case and extending in a direction parallel to said barrel axis, at least one rack rigid with said sliding piece and extending in a direction parallel to said barrel axis, at least one intermediate member movable between said racks in a direction parallel to said barrel axis, gear means carried by said member and meshing with both of said racks, said gear means including at least one pinion journalled in said member, and spring means between said member and said breech case for urging said member frontwardly.

2. A fire arm according to claim 1 in which said breech mechanism includes at least one breech block element movable in the direction of said barrel axis with respect to said breech case, the sliding piece mentioned in claim 1 being movable with respect to both said breech block element and said breech case.

References Cited in the file of this patent UNITED STATES PATENTS 1,837,512 Young et al. Dec. 22, 1931 2,581,395 Elfstrom Jan. 8, 1952 2,590,981 Lippert et a1. Apr. 1, 1952 FOREIGN PATENTS 610,258 Germany Mar. 6, 1935 535,570 Great Britain Apr. 15, 1941 897,562 France Mar. 26, 1945 574,352 Great Britain Ian. 2, 1946 

